1. Field of the Invention
The present invention relates to methods of treating subterranean zones using treating fluids whereby the swelling and migration of formation clays is prevented and maximum hydrocarbon productivity from the subterranean zone results.
2. Description of the Prior Art
Hydrocarbon producing subterranean zones penetrated by well bores are often completed and stimulated using aqueous treating fluids. Depending on the particular treatment to be conducted, the aqueous treating fluids can be viscosified by the addition of viscosity increasing gelling agents or by gelling agents which are cross-linked by cross-linking agents. For example, subterranean hydrocarbon producing zones are often fractured by pumping viscous fracturing fluids therein at rates and pressures such that one or more fractures are formed in the zones. Proppant particles such as graded sand for propping the fractures are suspended in at least a portion of the fracturing fluids so that the proppant particles are deposited in the fractures when the fracturing fluids are broken. That is, viscosity breakers are included in the fracturing fluids whereby the fracturing fluids revert to thin fluids which are returned to the surface. The proppant particles deposited in the fractures when the fracturing fluids lose their viscosities function to prevent the fractures from closing so that conductive channels are formed through which produced hydrocarbons can readily flow.
Hydrocarbon producing subterranean zones often include clays that swell in the presence of water and migrate through the zones whereby the permeabilities of the zones are reduced. In addition, the aqueous treating fluids utilized heretofore have often damaged the proppant particle packs formed in fractures whereby the production of hydrocarbons through the proppant particle packs is reduced. The damage has been the result of gelled treating fluids that form filter cake on the fracture faces which subsequently break up and flow into and remain in the proppant particle packs. In addition, viscous treating fluids utilized heretofore have included high loadings of viscosity increasing gelling agents. When such fluids have been broken, i.e, reduced in viscosity, a significant amount of polymer residue attaches to the proppant particle packs thereby further reducing the produced hydrocarbon conductivity of the packs.
Thus, there are continuing needs for improved methods of treating subterranean zones using treating fluids that produce maximum hydrocarbon productivity from the zones.